Recently, there has been a need for a polymer composition used for automobile tires to be prominent in reducing fuel consumption because automobiles have been increasingly required to have less fuel consumption owing to an increasing interest in environmental problems. As polymer compositions for automobile tires, those which contain conjugated diene-based polymers such as polybutadienes and butadiene-styrene copolymers and fillers such as carbon black have been used. For example, as the conjugated diene-based polymers, there have been known polymer compositions containing polymers which are produced by copolymerizing butadienes and styrene with a polymerization initiator of alkyl lithium and then modifying the ends of the copolymer chains with an acrylamide having a dialkylamino group (see, for example, Patent document 1), similarly, polymer compositions containing polymers which are produced by copolymerizing butadienes and styrene with a polymerization initiator of alkyl lithium and then modifying the ends of the copolymer chains with a bis(dimethylamino) methylvinylsilane (see, for example, Patent document 2), polymer compositions containing polymers which are produced by polymerizing butadienes or copolymerizing butadienes and styrene with a polymerization initiator of alkyl lithium and then modifying the ends of the resulting polymer chains with an alkoxysilane having a dialkylamino group (see, for example, Patent documents 3 and 4). Those have been proposed as polymer compositions promising a significant reduction in fuel consumption.
Patent document 1: JP-A-1-217047
Patent document 2: JP-A-1-217048
Patent document 3: JP-A-63-186748
Patent document 4: JP-A-2005-290355